Thermal Runaway Mechanism in Ni‐Rich Cathode Full Cells of Lithium‐Ion Batteries: The Role of Multidirectional Crosstalk

Crosstalk, the exchange of chemical species between battery electrodes, significantly accelerates thermal runaway (TR) of lithium‐ion batteries. To date, the understanding of their main mechanisms has centered on single‐directional crosstalk of oxygen (O2) gas from the cathode to the anode, underestimating the exothermic reactions during TR. However, the role of multidirectional crosstalk in steering additional exothermic reactions is yet to be elucidated due to the difficulties of correlative in situ analyses of full cells. Herein, the way in which such crosstalk triggers self‐amplifying feedback is elucidated that dramatically exacerbates TR within enclosed full cells, by employing synchrotron‐based high‐temperature X‐ray diffraction, mass spectrometry, and calorimetry. These findings reveal that ethylene (C2H4) gas generated at the anode promotes O2 evolution at the cathode. This O2 then returns to the anode, further promoting additional C2H4 formation and creating a self‐amplifying loop, thereby intensifying TR. Furthermore, CO2, traditionally viewed as an extinguishing gas, engages in the crosstalk by interacting with lithium at the anode to form Li2CO3, thereby accelerating TR beyond prior expectations. These insights have led to develop an anode coating that impedes the formation of C2H4 and O2, to effectively mitigate TR. This work addresses the fundamental causes of thermal runaway in lithium‐ion batteries, particularly in LiNi0.88Co0.1Al0.02O2/graphite full cells, a significant challenge for the electric vehicle industry. By employing synchrotron‐based high‐temperature X‐ray diffraction, mass spectrometry, and calorimetry, the intermediates that establish a self‐amplifying positive feedback loop are comprehensively identified through multidirectional crosstalk.